From 6fa956a7308306f370d3d9184f1baf34e96468ca Mon Sep 17 00:00:00 2001
From: Christoph Honal <christoph.honal@web.de>
Date: Sat, 18 Apr 2026 03:29:57 +0200
Subject: [PATCH] nixos/v4l2-relayd: Don't create dummy video device

---
 nixos/modules/services/video/v4l2-relayd.nix | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/nixos/modules/services/video/v4l2-relayd.nix b/nixos/modules/services/video/v4l2-relayd.nix
index bcf8725c845b..654c4a0aa272 100644
--- a/nixos/modules/services/video/v4l2-relayd.nix
+++ b/nixos/modules/services/video/v4l2-relayd.nix
@@ -221,6 +221,11 @@ in
       boot = mkIf ((length enabledInstances) > 0) {
         extraModulePackages = [ kernelPackages.v4l2loopback ];
         kernelModules = [ "v4l2loopback" ];
+        # Prevent v4l2loopback from auto-creating a device at load time. An
+        # unconfigured device has a degenerate framerate range that breaks
+        # GStreamer caps negotiation. All devices are created at runtime via
+        # v4l2loopback-ctl add in each instance's preStart instead.
+        extraModprobeConfig = "options v4l2loopback devices=0";
       };
 
       systemd.services = mkInstanceServices enabledInstances;